This invention relates generally to machine monitoring systems, and more particularly to a monitoring system calibration.
At least some known machines use capacitance probe-based clearance monitoring systems to measure member clearances. Specifically, one such monitoring system used in determining turbine blade tip clearance measurement uses a capacitance probe. To ensure the monitoring system is outputting correct clearance distance values, the monitoring system output may be periodically checked against a standard, such as, a calibration system of traceable accuracy characteristics. At least some known machines include rotating members that make access to portions of the monitoring system during machine operational conditions impracticable. Hence, the machine monitoring system may be calibrated during machine shutdown conditions. However, known calibration methods may introduce measurement inaccuracies related to characteristics inherent to a selected calibration probe measurement technology, to calibration probe placement in a different location than the monitoring system probe and/or to temperature expansion and rotational dynamics effects differences between the operating condition and the shutdown condition.